I’m standing on top of the motte and bailey of Plympton Castle in Devon. You know mottes and baileys from your school days, they’re those great towering lumps that the Normans threw up all over the country. And these walls are all that are left of the original castle that was built here over 700 years ago. Now in towns and villages, normally the medieval stuff disappears, it gets built over and we lose it, but here in Plympton the local people believe there’s enough of it left down there, for us to be able to work out the layout and the boundary of the medieval town that existed at the same time as that castle.